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With its TDI engines, Audi AG has been a leader in diesel development since 1989. Its latest technological innovation, the unique V8 TDI bears testimony to this fact. Common Rail A new injection system for the V8 engine Given that it can be integrated in existing engine concepts relatively easily, the common rail system is a new alternative injection system for modern diesel engines. As with any injection system, the common rail serves the following tasks Supplying the diesel engine with fuel Generating a high pressure for the injection cycle and distributing fuel to the cylinders Injecting a precisely calculated quantity of fuel into the cylinders at the right point in time. 2 Contents Page Introduction Common Rail System . 4 Components of the common rail Overview of the fuel feed process . 6 Low pressure fuel feed Roller cell pump . 8 Gear type pump . 9 High pressure fuel feed High pressure pump 10 Valve for fuel dosing N290 . 12 Fuel rail with high pressure control circuit 13 Regulating valve for fuel pressure N276 14 Fuel pressure sender G247 . 15 High pressure circuit 16 Valve controlled injection unit injector 17 Function of injector . 18 Engine management Mixture formation Commencement of fuel injection 20 End of fuel injection . 20 Pre injection cycle 21 Vacuum control 22 Double flow throttle valve 24 System overview 26 Function diagram . 28 Actuators and sensors Hall sender G40 30 Engine speed sender G28 Engine control unit J248/J494 32 Fuel temperature sender G81 . 33 Intake manifold pressure sender G71 33 Fuel bypass valve N312 34 Valve for fuel dosing N290 . 34 Important The Self Study Programme informs you about designs and Note functions. The Self Study Programme is not a Workshop Manual Please refer to the relevant Technical Literature for all maintenance and repair instructions. 3 Introduction Common Rail System The common